X.L. Wang G. H. Zhang and K.M Wu*
Hubei Collaborative Innovation Center for Advanced Steels,
International Research Institute for Steel Technology,
Wuhan University of Science and Technology, Wuhan 430081, China
A carbide free bainitic steel with a 0.3 wt.% carbon content were designed based on phase transformation theory. The microstructure and mechanical properties of this medium-carbon Si-rich steel subjected to isothermal bainitic transformation at
300-360 °C were investigated by thermal simulator, optical microscopy, X-ray diffraction, electron microscopy and tension and impact tests. Results show that the microstructure composed of bainitic-ferrite, carbon enriched film-like austenite and martensite/austenite blocks. The high levels of strength accompanied by reasonable ductility and toughness is achieved, and the toughness deterioration in high carbon bainitic steels was effectively avoided. The tensile strength 1324-1391 MPa are obtained and accompanied by the elongation 11.7-16.6 % and the Charpy-V impact energy 34-39 J.
Alloys design; Isothermal transformation; Microstructure; Retained austenite; Mechanical properties